Cut bread into cubes, toast at 325°F for 10–12 minutes if soft, and add to a large mixing bowl.
Cook kielbasa in a skillet over medium heat for 5–7 minutes until browned; transfer to the bowl.
Add butter to the same skillet, then sauté onion and celery for 6–7 minutes.
Stir in garlic and cook 1 minute.
Season with salt, pepper, and dried marjoram; transfer to the bread mixture.
Stir in optional sauerkraut, apples, parsley or dill.
Add fresh sage, thyme, and additional dried marjoram if needed.
Whisk warm broth with beaten eggs and pour over stuffing mixture.
Gently stir until evenly moistened, adding more broth if needed.
Grease a 9×13 baking dish with butter or olive oil.
Spread stuffing mixture evenly in the dish, cover with foil, and bake at 375°F for 30 minutes.
Uncover and bake an additional 15–20 minutes until the top is golden and crisp.
Rest 5 minutes before serving.